The oil and gas industries separate linear paraffins from branched paraffins to aid in the production of high quality fuels. For instance, gasoline with a high octane rating results in less engine knocking in internal combustion engines and improved engine performance. Diesel engines, on the other hand, perform optimally with high cetane fuel, which readily ignites under pressures typically observed in a diesel engine. Separating paraffins is important to these industries because the octane rating and cetane rating are directly related to the amount of linear paraffins and branched paraffins present in the fuel. Now that reducing harmful emissions is a matter of global concern, processes that separate linear paraffins from branched paraffins have become increasingly important.
The separation of linear paraffins from branched paraffins, however, remains one of the most intensive and challenging separations of today. Fractionation or distillation processes are employed to separate paraffins, but these processes consume large amounts of energy. Adsorption through zeolite molecular sieves processes are also employed to accomplish the separation, but these processes are less efficient as 3% to 4% of branched paraffins diffuse and/or adsorb on the adsorbent. Metal-organic frameworks offer great potential as an adsorbent or membrane, given the ability to tune or control pore aperture and the potential to alter adsorption and diffusion properties via cation exchange. However, to date, there have been no reports of achieving a complete separation of linear paraffins from branched paraffins using a metal-organic framework.